The present invention relates to a brake cylinder unit with which a normal-service brake and a spring brake used as a parking brake, etc., can be operated, and relates in particular to brake cylinder unit that can shorten the axial length.
In addition to a normal-service brake unit that acts with compressed air, a spring brake unit that acts by means of spring force without any compressed air is used in cases where a railway car is stopped for a long period of time, for the truck brake unit of for example railway cars. When one configures the truck brake unit by installing the normal-service brake unit and the spring unit separately and independently, installation space becomes necessary.
Accordingly, a brake cylinder unit that composes an air brake unit and a spring brake unit in a monobloc has been developed, such that it makes both brake units act through the medium of the same piston rod.
For example, as shown in FIG. 15, in Japanese Public Patent Disclosure Bulletin S55-160646, there is disclosed a brake cylinder unit (90) equipped with (a) a normal-service brake means (91) that possesses a first piston (93) wherein a rod (931) protrudes, and a first spring (95) acts in opposition to a first action chamber (94), and wherein the first piston (93) moves in the brake direction by overcoming the impetus of the first spring (95) when a pressure fluid acts on the first action chamber (94), and (b) a spring brake means (92) that possesses a second piston (98) wherein the rod (931) passes completely through and that is provided such that it can move in the axial direction of the rod (93), and wherein a second spring (97) acts in opposition to a second action chamber (96), and the second piston (98) moves in the brake direction due to the impetus of the second spring (97) when the pressure fluid ceases to act on the second action chamber (96), and a mating part (932) whereby the second piston (93) is in contact with the rod (931) has been formed.
When the pressure fluid acts on the first action chamber (94) of the normal-service brake means (91), the first piston (93) and the rod (931) move in the brake direction in opposition to the first spring (95), and it becomes the normal-service brake unit shown in the figure. In this normal-service brake unit, when the pressure fluid ceases to act on the first action chamber (94) of the common-service means (91) and the second action chamber (96) of the spring brake means (92), the second piston (98) moves in the brake direction along the rod (931) due to the second spring (97). When this second piston (98) contacts the mating part (932), the impetus of the second spring (97) is transmitted to the rod (931), and the spring brake acts instead of the normal-service brake.
As shown in Japanese Public Patent Disclosure Bulletin S55-160646, in the event that a mating part (932) is formed on the rod (931), the mating part (932) is provided by making it capable of sliding on the tip side of the rod (931) such that the mating part (932) does not come into contact with the second piston (98), when one relaxes the normal-service brake means (91) and shortens the rod (931) by means of the impetus of the first piston (95). For this purpose, it is necessary for the second piston (98) to move along the rod (931) by just the distance L shown in the figure, until the second piston (98) is in contact with the mating part (932) of the rod (931). As a result, there is the problem that the axial direction length of the brake cylinder (90) becomes longer, by just that amount equivalent to the length L.
In addition, in Utility Model Registration Bulletin H08-5881, there is proposed a brake cylinder unit that is fitted to a sleeve, of which one end can contact the second piston (98) on the outer periphery of the rod (931), and of which the other end can contact the stage part of the large bore part that has been provided on the rod (931), instead of the mating part (932). However, since it is possible to fit only a sleeve with a length to the extent for which the first piston (93) and the rod (931) can be shortened during the releasing of the normal-service brake means (91), it is necessary for the second piston (98) to move a considerable distance until it causes the spring brake (92) act, just as in the case of Japanese Public Patent Disclosure Bulletin S55-160646, and there is the problem that the axial direction length of the brake cylinder unit (90) becomes long.
Accordingly, the present invention takes as its purpose the provision of a brake cylinder unit whereby both the normal-service brake and the spring brake that is used as a stop brake, etc., can act, and that moreover can shorten the axial length.
The invention in the first embodiment for attaining the above-mentioned purpose is a brake cylinder unit, being a brake cylinder unit with which both a normal-service brake and a spring can be operated that is equipped with (a) a normal-service brake means that possesses a first piston wherein a rod protrudes, and a first spring acts in opposition to a first action chamber, and wherein the above-mentioned first piston moves in the brake direction by overcoming the impetus of the above-mentioned first spring when a pressure fluid acts on the above-mentioned first action chamber, and (b) a spring brake means that possesses a second piston wherein the above-mentioned rod passes completely through and that is provided such that it can move in the axial direction of the above-mentioned rod, which is characterized by the fact that a second spring acts in opposition to a second action chamber, and the above-mentioned second piston moves in the above-mentioned brake direction due to the impetus of the above-mentioned second spring when the pressure fluid ceases to act on the above-mentioned second action chamber, wherein there is provided a clutch means that links the above-mentioned rod and the above-mentioned second piston when the pressure fluid ceases to act on the above-mentioned second pressure chamber, and the above-mentioned second piston begins to move towards the above-mentioned rod.
According to the above-mentioned composition, when the second action chamber ceases to act, and the second piston starts to move towards the rod, the rod and the second piston are linked by the clutch means, and the spring brake acts on the rod through the medium of the second piston. Owing to this, the amount of movement of the second piston is smaller.